Robust numerical solution for assessing corrosion of reinforced concrete structures under external power supply

Impressing current is a popular technique to adjust corrosion behaviors of structures, both in academic investigation and engineering practice. Focusing on the specific problem, this paper presents a robust solution strategy for analyzing corrosion of reinforced concrete structures, under both voltage-controlled and current-controlled power supply. Following fundamental electrochemistry, a nonlinear numerical model incorporating field and global variables is developed, where the ways of considering power supplies with different controlling modes are presented. To tackle the essential global variable to problems under current-controlled power supply, a pseudo discretization method is newly developed to facilitate the highly nonlinear finite element analysis. Given moisture-induced nonuniform concrete resistivity, the moisture field in concrete is also modelled and solved together with the corrosion propagation through a staggered solution scheme. The proposed approach is carefully validated against a variety of reported experiments. Moreover, by directly controlling steel passivation state, the influence of steel depassivation extent on the cathodic protection performance for aging reinforced concrete structures under different saturation degree is numerically investigated for the first time. It is discovered that the protection effectiveness is closely related to the steel depassivation state. It is also revealed that the influence of concrete saturation degree on protection performance in a current-controlled system is generally more complex than that of a voltage-controlled system.